How to Read and Use Roman Numerals
Have you ever noticed at the end of a movie after the credits they has something that looks like this MCMLXXVIII. These seemingly meaningless letters are Roman Numerals. They are a simple combination of letters that represent the number 1978. The first 12 numbers are represented as follows: I, II, III, IV, V, VI, VII, VIII, IX, X, XI, XII.
The use of “sticks” or later stick symbols was how people initially counted. That is why the first three numbers are I’s. Each “I” represents a stick. In the early Roman Empire the number four was represented as four sticks, side by side: IIII.
The V for 5 comes from the number of fingers in your hand. When the hand is outstretched with the thumb and pinky pointing opposite directions and the others folded, we have what almost looks like a V.
The X for ten was used when you have two hands crossing each other.
The system is simple to use… You keep adding smaller symbols side by side until you get to the next value in symbols then you replace all the smaller value symbols for the larger value symbol. For example:
I (one stick) = 1
II (two sticks) = 2
III (three sticks) = 3
IIII (four sticks) = 4
IIIII (five sticks replaced with V) = 5
IIIIII (six sticks we package the first five and replace them with V and write down the rest) VI = 6
IIIIIII (seven sticks… gives us VII) = 7
This works for bigger values as well:
X = 10
XX = 20
XXX = 30
The list of Roman Numbers is:
You want to write 15… You would use the symbol for 10, X, and the symbol for 5, V, and get XV.
You want to write 101… You would use the symbol for 100, C, and the symbol for 1, I, and get CI.
You want to write 2232… You would use the symbol for 1000, M, and write it twice; the symbol for 100, C, and write it twice; the symbol for 10, X, and write it three times; the symbol for 1, I, and write it two times. The result is MMCCXXXII.
The subtraction principle:
The next development in Roman Numerals came with the use of subtraction. To reduce the number of letters it was deemed that when a small symbol appears to the left of a larger number, then you subtract that value from the number on the right.
For example: IIII, 4, became IV. The I, 1, subtracts from the V, 5, to give us IV or 4. The number nine would be written as IX (10 – 1= 9) instead of the lengthy version VIIII.
IV = 4 versus IIII
IX = 9 versus VIIII
IL = 49 versus XXXXVIIII
VL = 45 versus XXXXV
IC = 99 versus LXXXXVIIII
VC = 95 versus LXXXXV
XC = 90 versus LXXXX
The key is to reduce the number of symbols. That is why VX (10 – 5) would not work for 5, V. There are more symbols in VX versus V for the value of 5.
1) 91 is found by taking 90, XC, and adding 1, I, to it. This gives us XCI.
2) 1996 is found by taking 1000, M, 995, VM (1000-5), and I, 1, and listing them all down… MVMI.
3) 3444 is found by taking 3 M’s, CD (500 – 100), XL (50 – 10), and IV (5 - 1). We have MMMCDXLIV.
Using bars to represent larger numbers:
To show 5000, they would take the symbol for 5, V, and add a bar across it. The bar acted as a place holder for larger digits.
Take for example a nasty number like this: 239,480,216 = To solve this take each group of three numbers separately. The number 239 becomes CC, for the 2, XXX, for the 3, IX, for the 9. That is CCXXXIX. The next grouping is 480 becomes, CD, for the 4, LXXX, for the 8. This gives us 480. (Note the zero is not needed since the bar over 480 tells us it is in the thousands place.) Lastly, 216 can be written as CC, for the 2, X, for the 10, and VI for the 6.
With the use of seven symbols, the subtraction principle, and bars of their numbers, the Romans could write relatively large numbers. The weakness with the system was when one needed extremely large numbers. That is why the Roman system gave way to the current Arabic numbering system that we use today for most uses. The graph below lists a few key Roman Numbers less than 1000.
Today you will find Roman numbers are occasionally used. When you do, hopefully this article will help to interpret them easier.
Hope this Helps and Take care.